酶是一类生物催化剂，生物的生命活动离不开酶的催化。下面有关酶的叙述正确的是[ ]

A．因为酶的催化效率高，故酶促反应速度与酶的浓度无关

B．有些酶由蛋白质构成，有些酶则是由脂质或核酸构成

C．酶促反应能释放出更多的能量

D．RNA聚合酶的最终水解产物是氨基酸

Some of the low-end Made-in-China mechanical-electronic products are not selling well in export market as compared with what are termed as high-end ones.

A．on export market

B．in exporting market

C．in exported market

D．in the export market